Bump actions/checkout from 5 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/build-documentation.yml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Set up Python 3.11
       uses: actions/setup-python@v6
       with:

.github/workflows/pre-commit-ci.yml

@@ -14,7 +14,7 @@ jobs:
   pre-commit-ci:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 0 
     - name: Set up Python

.github/workflows/publish-to-pypi.yml

@@ -23,7 +23,7 @@ jobs:
     permissions:
       id-token: write
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Set up Python
       uses: actions/setup-python@v6
       with:

.github/workflows/smoke-test.yml

@@ -23,7 +23,7 @@ jobs:
         python-version: ['3.10', '3.11', '3.12', '3.13']
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v6
       with:

.github/workflows/testing-and-coverage.yml

@@ -19,7 +19,7 @@ jobs:
         python-version: ['3.10', '3.11', '3.12', '3.13']
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v6
       with:
@@ -40,7 +40,7 @@ jobs:
   test-lowest-versions:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Set up Python 3.10
       uses: actions/setup-python@v6
       with: